How to create a curve from a mesh?
So what you can do to convert it to a curve:

Go in Edit mode, as it is triangulate, select all and untriangulate with AltJ:



Also, you have ripped edges so AltM to merge by distance:



Select an edge loop, separate with P:



Go into the Object menu to convert the mesh to curve:



To simplify the curve, you can enable the Simplify Curves addon, then in Edit mode press ShiftA &gt; Curve Simplify, in the Operator box choose an Error value of 1 and Output &gt; Bezier, it's going to create a simplified version of your curve:



Press V if you ever want to switch from Automatic handles to Aligned:



Now you can do whatever you want with this curve: